The present invention relates to a multiplex system of the type which uses a central controller and a plurality of remote stations to control a plurality of motors in response to motor control signals.
One feature commonly available in modern automobiles is that of a power seat which uses electric motors to position the seat to suit an individual driver. Often, such power seats include memory systems which allow a particular seat position to be stored. Means are provided for automatically returning the power seat to the stored position. In the past, such memory seat systems have also included means for storing a selected position of the outside mirrors, and automatically moving the outside mirrors to the previously stored position.
One approach to implementing the memory seat functions described above is to provide an absolute position encoder for each axis of travel of the power seat motors and the mirror motors. For example, potentiometers can be linked to each motor axis to provide an analog voltage that can be used as a measure of the position of the seat or mirror along the respective axis. This approach provides the disadvantage that it requires position encoders to implement the memory seat function. These encoders increase the cost and complexity, and reduce the reliability of the overall system.
For some time there has been an interest in utilizing multiplex motor control systems in vehicles. Brittain U.S. Pat. No. 4,293,947 provides one example of such a system. In spite of this interest in multiplex systems, currently available multiplex systems do not exploit the full potential of the multiplex system to enhance motor control, and in particular to provide a memory seat function without materially increasing the cost or hardware complexity of the system.